Course E : Soft Materials - Welcome to the SRCF -...

Dr James Elliott

Course E : Soft Materials

Materials Science & MetallurgyEaster Term 2006

Natural Sciences Tripos Part IB

[email protected]

Copyright © 2002 University of Cambridge. Not to be quoted or copied without permission.

IB Materials & Metallurgy Course Outline 2005-06

Michaelmas Term

Course A : Phase Transformations

Course B : Materials and the Environment

Lent Term

Course C : Biomechanics

Course D : Electrical Properties of Materials

Easter Term

Course E : Soft Materials


Course E synopsis (EH1)Introduction. What are soft materials? Why are they of interest to materials scientist? Examples of soft systems: polymers, foams, granular media, colloids, and liquid crystals.Polymers and polymer chains. Some common examples, market, comparative costs, applications. Some definitions. Typical backbones, side groups, branching, cross-linking. Thermoplastics and thermosets. Molecular architecture. Structural isomerism, configurational isomerism. Tacticity. Copolymers.Semi-crystalline polymers. Factors influencing crystallisation, crystal structures, spherulites. Measurement of crystallinity, X-ray diffraction. Bragg and Scherrer equations. Influence of structure on melting point.Amorphous polymers. Chain conformations, chain torsion, thermodynamics of chains Introduction to differential scanning calorimetry. The glass transition: influence of structure, determination ofTg, effect of time scale. Chain alignment and birefringence. Hermans orientation function.


Course E synopsis (EH1)How are polymers made? Chain growth (by addition): initiation, propagation, termination. Functionality. Step growth. Statistics of step growth. Molecular mass: definitions and measurement. Cross-linking: heavily cross-linked thermosets and vulcanisation of rubbers.Characterisation of polymers by infra-red spectroscopy and mass spectrometry.Polymers in use. Structural influences on properties. Stiffness and yielding. Basic techniques for polymer processing. Copolymers and blends. Complex phase behaviour of amphiphilic copolymers, and methods for probing structure in partially ordered phases. Some applications in pharmaceutical and cosmetic industries.Cellular structures (foams). Formation and Ostwald ripening. Surface tension effects. The Young and Young-Laplace equations, Plateau’s rules and foam structure. Mechanical behaviour of regular foams.The Voronoi tessellation and the relationship between cellular structure and granular packing.


Course E synopsis (EH1)

Granular materials (powders). Particle packing as a function of size distribution and mechanical properties of powder particles. Granular flow and segregation. The Brazil-Nut effect. Powder processing methods. Some applications in pharmaceutics and powder metallurgy.Colloidal matter. Entropy-driven phase separation. Depletion forces. Micelles, microemulsions, solubilization and mechanisms of detergency.Liquid crystals. Revision of isotropic and nematic phases from IA. The nematic order parameter, and link with Hermans orientation function for polymeric systems. Maier-Saupe and Onsager theories for isotropic-nematic phase transition. The smectic phases.


Course E recommended reading (EH2)Key General Texts

I. W. Hamley, Introduction to Soft Matter, Wiley, 2000 [Pf55, UL: 360:7.c.200.1]C. Newey and G. Weaver, Materials principles and practice, Butterworths, 1990 [AB125]

PolymersN.G. McCrum, C.P. Buckley and C.B. Bucknall, Principles of polymer engineering, 2nd ed., OUP, 1997 [AN6d.57, AN6d.57a TRIPOS]N.J. Mills, Plastics: microstructure, properties and applications, 2nd ed., Arnold, 1993 [AN6c.126]F. Rodriguez, Principles of polymer systems, 2nd ed., McGraw-Hill, 1982 [AN6a.30, An6a.64 TRIPOS]F. J. Baltá-Calleja and C. G. Vonk, X-ray Scattering of Synthetic Polymers, Elsevier, 1989 [NbC85]


Course E recommended reading (EH2)Foams

L. J. Gibson and M. F. Ashby, Cellular solids : structure and properties, Pergammon Press, 1988 [Ka48, Ka96 TRIPOS]D. Weaire and S. Hutzler, The physics of foams, OUP, 1999 [Ka99]

Granular materialsR. M. Nedderman, Statics and kinetics of granular materials, CUP, 1992 [Ka55/Ka55a]

ColloidsI. W. Hamley, Introduction to Soft Matter, Wiley, 2000 [Pf55, UL: 360:7.c.200.1]

Liquid crystalsS. Chandrasekhar Liquid Crystals 2nd edition, 1992, CUP [Ng66]A. M. Donald and A. H. Windle, Liquid Crystalline Polymers, CUP, 1992 [Ng120, UL: 361:82.c.95.1052]


Course E practicals (EH2) and TLPs (EH3)

EP1 : Crystallisation of polymers– Optical microscopy, SEM and mechanical testing

EP2 : Chain Alignment and Birefringence– Quantification of stress-induced changes in polymer morphology using

optical microscopy and X-ray diffraction

EP3 : Functionality of a Resin System (ASSESSED)– Network formation in resins using infra-red spectrometry and viscosity

measurements

There will be four question sheets (EQ1, EQ2, EQ3, EQ4) issued for this course.TLPs: “Crystallisation of Polymers”, “Recycling of Polymers”http://www.doitpoms.ac.uk/tlplib


Some examples of polymer structures (EH4)

Tg = 4ºC

Tm = 195ºC


Stiffness and cost (EH5)


Market shares for thermoplastics (EH5)


Polyethylene conformations


Stereoisomerism (EH6)


Tacticity in PVOH

ISO TACTIC

SYNDIOTACTIC

ATACTIC


Classification of copolymers (EH6)


Polyethylene chains spontaneously chain-fold


Crystal structure of polyethylene (EH8)


Spherulite formation in polymers (EH8)


Spherulite structure (EH9)


Spherulites – Maltese cross and banding


Relationship between Tm and Tg (EH11)


Measuring chain orientation by X-ray diffraction

equator

meridian

equator


Azimuthal intensity plot

0

20

40

60

80

100

120

140

-40 60 160 260 360

Azimuthal angle (phi)

Inte

nsity

(a.u

.)

UnorientedOriented

Measuring chain orientation by X-ray diffraction

φH200 [unoriented] = 0.093

H200 [oriented] = –0.320⇒ chain packing normal to chain axis (EH9)

Course E : Soft Materials - Welcome to the SRCF -...

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